1. Field of the Invention
The present invention relates to metathesis reactions between two or more solid compounds and more particularly to metathesis reactions between two salt compounds for synthesizing refractory materials within seconds.
2. Description of the Prior Art
There has been a great need to find new methods of synthesizing refractory materials. Especially important are methods which enable refractory material to be synthesized more easily than by use of traditional high temperature reactions between elements. Since solid-solid diffusion between elements is slow, traditional syntheses generally require temperature of from 500.degree. C. to greater than 3000.degree. C. and time periods of from days to many weeks in order to produce desired refractory materials. Even after extensive heating for long periods of time these refractory materials may still contain unreacted starting materials, unwanted phases and/or poor stoichiometry.
U.S. Pat. No. 4,279,737, entitled Hydro-Desulfurization Over Catalysts Comprising Chalcogenides of Group VIII Prepared by Low Temperature Precipitation from Nonaqueous Solution, issued to Russell R. Chianelli and Theresa Pecoraro on Jul. 21, 1981, teaches a method which is described for the preparation of chalcogenides of ruthenium, rhodium, osmium and iridium transition metals of the Periodic Table of the Elements which includes mixing in the absence of an aqueous solvent a Group VIII transition metal salt with a source of chalcogenide. The chalcogenide is selected from the group consisting of sulfur, selenium, tellurium and mixtures thereof, yielding a precipitate of the formula MX.sub.y wherein M is selected from the group consisting of ruthenium, rhodium, osmium and iridium, X is sulfur, selenium, tellurium and mixtures thereof and y is a number ranging from about 0.1 to about 3, preferably 0.1 to about 2.5. By the practice of the nonaqueous synthesis technique, Group VIII chalcogenides are prepared which are finely divided, have a high surface area, small particle size and small crystallite size which are also free of excess sulfur, water and/or hydrolysis products. This technique also permits the preparation of a heretofore unobtainable composition, layered stoichiometric osmium disulfide. The precipitates which result as a consequence of the instant process may be cleansed of any anion salt coproduct by any technique common to the art, pumping under vacuum being one such technique, washing with a suitable solvent being another. Compounds of the formula MX.sub.y wherein M, X and y are as defined above, prepared by the low temperature, nonaqueous precipitation technique herein disclosed are superior sulfur-tolerant catalysts in catalytic processes, for example, hydrodesulfurization, hydrodenitrogenation, hydroconversion, hydrogenation.
U.S. Pat. No. 4,288,422, entitled Method of Preparing Chalcogenides of Group VIII by Low Temperature Precipitation from Nonaqueous Solution, the Products Produced by Said Method and Their Use as Catalysts, issued to Russell R. Chianelli and Theresa A. Pecoraro on Sep. 8, 1981, teaches a method which described for the preparation of chalcogenides of ruthenium, rhodium, osmium and iridium transition metals of the Periodic Table of the Elements which includes mixing in the absence of an aqueous solvent a Group VIII transition metal salt with a source of chalcogenide. The chalcogenide is selected from the group consisting of sulfur, selenium, tellurium and mixtures thereof, yielding a precipitate of the formula MX.sub.y wherein M is selected from the group consisting of ruthenium, rhodium, osmium and iridium, X is sulfur, selenium, tellurium and mixtures thereof and y is a number ranging from about 0.1 to about 3, preferably 0.1 to about 2.5. By the practice of the nonaqueous synthesis technique, Group VIII chalcogenides are prepared which are finely divided, have a high surface area, small particle size and small crystallite size which are also free of excess sulfur, water and/or hydrolysis products. Layered stoichiometric osmium disulfide is prepared by this technique. The precipitates may be cleansed of any anion salt coproduct by any technique common to the art. Compounds of the formula MX.sub.y thus prepared are superior sulfur-tolerant catalysts in catalytic processes, for example, hydro-desulfurization, hydrodenitrogenation, hydroconversion, hydrogenation.
U.S. Pat. No. 4,308,171, entitled Method of Preparing Di and Poly Chalcogenides of Group VIIb by Low Temperature Precipitation from Nonaqueous Solution and Small Crystallite Size Stoichiometric Layered Dichalcogenides of Rhenium and Technetium, issued Martin B. Dines, Russell R. Chianelli and Theresa A. Pecoraro on Dec. 29, 1981, teaches a method whereby finely divided, small particle (0.1 micron or less) small crystallite (about 50 Angstrom times 100 Angstrom or less) chalcogenides of manganese, rhenium and technetium are described. These compositions are prepared by mixing in the absence of an aqueous solvent, a manganese, rhenium or technetium salt with a source of chalcogenide yielding a precipitate. The manganese, rhenium or technetium salt and the source of chalcogen can be mixed either neat or in the presence of a nonaqueous aprotic solvent. The precipitate which results before removal of the anion salt is a finely divided product. In the case of rhenium dichalcogenide the product possesses a layered structure. The anion salt may be removed by any technique common to the art, pumping under vacuum being one such technique, washing with a suitable solvent being another. A method is described for the preparation of di- and poly-chalcogenides of the formula MX.sub.y wherein M is a metal selected from the group consisting of manganese, rhenium and technetium, X is a chalcogen selected from the group consisting of sulfur, selenium, tellurium and mixtures thereof, and y is a number ranging from about 1.5 to about 4, preferably about 2, comprising the low temperature, nonaqueous precipitation of said MX.sub.y compounds from mixtures of the salts of the manganese, rhenium and technetium. The precipitation occurs in the absence of aqueous solvents. The process of the instant invention permits the preparation of materials uncontaminated by water, oxygen or hydrolysis products.
U.S. Pat. No. 4,323,480, entitled Method of Preparing Di and Poly Chalcogenides of Group IVb, Vb, Molybdenum and Tungsten Transition Metals by Low Temperature Precipitation from Non-aqueous Solution and the Product Obtained by Said Method, issued to Martin B. Dines and Russell R. Chianelli on Apr. 6, 1982, teaches the finely divided, high surface area, small crystallite (0.1 micron or less) di- and poly-transition metal chalcogenides are prepared by mixing in the absence of an aqueous solvent a transition metal salt with a source of chalcogen yielding a precipitate. The salt and the chalcogen source can be mixed either neat or in the presence of a nonaqueous solvent. The precipitate which results before removal of the anion salt is a finely divided product.
U.S. Pat. No. 4,368,115, entitled Catalysts Comprising Layered Chalcogenides of Group IVb-Group VIIb Prepared by a Low Temperature Nonaqueous Precipitate Technique, issued to Russell R. Chianelli, Theresa A. Pecoraro and Martin B. Dines on Mar. 11, 1981, teaches processes for the catalytic treatment of hydrocarbon feedstreams containing organic sulfur which include contacting the feedstream with a catalyst for a time at a temperature and pressure sufficient to effect the desired catalytic change on the feedstream. The improvement includes using as the catalyst a layered composition of the formula MX.sub.y wherein M is a transition metal selected from the group consisting of Group IVb, Vb, VIb, VIIb and uranium, X is a chalcogen selected from the group consisting of sulfur, selenium, tellurium, and mixtures thereof, y is a number ranging from about 1.5 to about 3. The catalyst is prepared by reacting neat or in the presence of a nonaqueous solvent a Group IVb to VIIb or uranium metal salt, and a source of sulfide, selenide or telluride ions, and mixing the reactants at temperatures below 400.degree. C. and at atmospheric pressures. The catalyst may be isolated by filtration and washing with excess solvent (when one is used) or by vacuum pumping any volatile coproduced anion salt. Preferably the chalcogenide is sulfur and y is about 1.5 to about 2. The catalytic processes which are benefited by the use therein of the above-described compositions are hydrodesulfurization, hydrodenitrogenation, hydroconversion and hydrogenation run in the presence of hydrogen or a hydrogen donor solvent.
U.S. Pat. No. 4,399,115, entitled Synthesis of Silicon Nitride, issued to Kimihiko Sato, Kunihiko Terase and Hitoshi Kijimuta on Aug. 16, 1983, teaches a process for synthesizing silicon nitride by reacting a silicon halide and ammonia at a high temperature, which is characterized in that at least while the reaction product is amorphous, hydrogen and chlorine are burned in the reaction zone where a halogen containing inorganic silicon compound and ammonia are reacting, and the reaction of the reactants is effected by the heat of combustion thus obtained.
U.S. Pat. No. 4,416,863, entitled Method for Synthesizing Amorphous Silicon Nitride, issued to Kimihiko Sato, Kunihiko Terase, Hitoshi Kijimuta and Yukinori Ohta on Nov. 22, 1983, teaches a method for synthesizing amorphous silicon nitride in which wherein silicon halide and ammonia are reacted in a reaction vessel at a high temperature in the absence of oxygen to synthesize powder of amorphous silicon nitride. The powder is then separated from a gas containing therein gaseous ammonia halide which has been produced simultaneously with the amorphous silicon nitride by use of a collecting means, includes directly mixing, in advance of the separation, cool gas containing therein neither oxygen nor moisture into the gas to cool down the powder and gas so that both substances may be put in the collecting means without deposition of ammonium halide to the inner wall of the reaction vessel, and other component parts.
U.S. Pat. No. 4,731,235, entitled Method of Making Silicon Nitride, issued to John L. Schrader, Jr. and Patience G. Dowd on Mar. 15, 1988, teaches the manufacture of silicon nitride powder by the vapor phase reaction of a silicon halide with ammonia at an elevated temperature in a flowing system, oxygen content of the silicon nitride is controlled by preventing entry of room air into the reaction means and by feeding wet nitrogen into the system at about the exit end of the reaction means.
U.S. Pat. No. 4,812,301, entitled Production of Titanium Nitride, Carbide, and Carbonitride Powders, issued to Charles F. Davidson, Monte B. Shirts and Donna D. Harbuck on Mar. 14, 1989, teaches a process for producing substantially oxygen-free titanium carbide, nitride or carbonitride in powder form which includes treating a gas phase reaction mixture of titanium halide, desirably TiCl.sub.4, a reductant vapor, desirably sodium or magnesium, and a reactive gas capable of furnishing carbon, nitrogen or mixtures thereof at the reaction temperature, desirably nitrogen, methane or ammonia, to a temperature in the range from 500.degree. C. to 1250.degree. C., preferably 800.degree. C. to 1100.degree. C., whereby the titanium halide is substantially simultaneously reduced and carbided, nitrided or carbonitrided. The process may also be practiced using volatile metal halides of metals such as zironium, hafnium, vanadium, niobium, tantalum and silicon for forming substantially oxygen-free carbides, nitrides or carbonitrides thereof in powder form.
U.S. Pat. No. 4,859,443, entitled Preparation of Silicon Nitride Powder, issued to Laszlo Marosi on Aug. 22, 1989, teaches about a silicon nitride powder which is prepared in a gas-phase reaction by reacting silicon tetrachloride with ammonia at above 500.degree. C. in a fluidized bed of silicon nitride particles. An amorphous silicon nitride having a BET specific surface area of greater than 50 m.sup.2 /g is used at the beginning of the reaction. The resulting silicon nitride is then separated from the ammonium chloride simultaneously formed.
U.S. Pat. No. 4,859,639, entitled Process of Making Amorphous Silicon Nitride Powder, issued to Hans-Josef Sterzel on Aug. 22, 1990, teaches in amorphous silicon nitride powder, from 0.5 to 40 mol % of the silicon are replaced by one or more of the elements boron, aluminum, yttrium, lanthanum, titanium, zirconium, tungsten and molybdenum. The powder is obtained by reacting the halides of the corresponding elements, which are dissolved in an inert organic solvent in the particular ratio desired, with ammonia. The solid reaction product formed is separated off from the liquid phase and treated at from 800.degree. C. to 1000.degree. C. The powder is particularly suitable as a starting material for the production of sintered articles.
U.S. Pat. No. 4,929,432, entitled Process for Producing Crystalline Silicon Nitride Powder, issued to Wei-Ming Shen on May 29, 1990, teaches a process for producing crystalline silicon nitride powder by a gas phase reaction of ammonia (NH.sub.3) and silane (SiH.sub.4) with a molar ratio of 7:1 or above at a temperature of 900.degree. C. or above and the heating the as-reacted amorphous powders at a temperature of 1350.degree. C. to 1800.degree. C. to convert the powders to a highly pure and submicron crystalline silicon nitride powder comprising at least a 90% alpha-Si.sub.3 N.sub.4 phase.
U.S. Pat. No. 4,944,930, entitled Synthesis of Fine-Grained Alpha-Silicon Nitride by a Combustion Process, issued to J. Holt, Donald D. Kingman and Gregory M. Bianchini on Jul. 31, 1990, teaches a combustion synthesis process for the preparation of alpha-silicon nitride and composites thereof is disclosed. Preparation of the alpha-silicon nitride comprises the steps of dry mixing silicon powder with an alkali metal azide, such as sodium azide, cold-pressing the mixture into any desired shape, or loading the mixture into a fused, quartz crucible, loading the crucible into a combustion chamber, pressurizing the chamber with nitrogen and igniting the mixture using an igniter pellet. The method for the preparation of the composites includes dry mixing silicon powder (Si) or silicon dioxide (SiO.sub.2), with a metal or metal oxide, adding a small amount of an alkali metal azide such as sodium azide, introducing the mixture into a suitable combustion chamber, pressurizing the combustion chamber with nitrogen, igniting the mixture within the combustion chamber, and isolating the alpha-silicon nitride formed as a reaction product.